The entire main cast is going to die, guaranteed. We've already seen a bit in the trailer where Jyn is hobbling along a walkway, clearly injured, when a fucking tie fighter pulls up on her ass

If many Bothans died to get plans when the Emperor deliberately allowed them to steal the plans then there's no way they make it. Plus if they needed Leia to deliver them I think that implies that they couldn't, because they're all dead.

I actually believe it. There's gonna be some "heroic sacrifice" and you're gonna get some little speech given by a rebel leader years later about how the team saved the universe. It will be like the Halo: Reach ending. The protagonists die but you know it's so the good guys will win in the end.